Most Common Mitsubishi Check Engine Codes (Outlander, Eclipse, Lancer, Galant, and Montero)

Understanding Mitsubishi Check Engine Codes

Mitsubishi vehicles use a mix of proprietary and shared powertrain components. The Outlander and Eclipse Cross use Mitsubishi's own 2.4L and 2.5L four-cylinder engines along with a JATCO CVT transmission. The Lancer Evolution used the legendary 4B11 turbocharged engine, while older Lancers and Galants used the 4G63, 4G64, and 4G69 inline-four engines. The Montero Sport used the 3.0L and 3.5L V6. Mitsubishi vehicles tend to be reliable but have specific patterns around EVAP system sensitivity, catalytic converter longevity, and CVT transmission issues. The check engine light on Mitsubishi vehicles is triggered more readily than on some competitors, particularly for minor EVAP and emissions faults. Understanding which codes require immediate attention versus monitoring can save significant money on unnecessary repairs.

P0171 -- System Too Lean (Bank 1)

P0171 on Mitsubishi vehicles indicates a lean fuel condition. On the Outlander with the 2.4L engine, the most common cause is a dirty or failing mass airflow (MAF) sensor ($50-$80). Cleaning the MAF sensor with dedicated MAF cleaner spray ($8-$12) should be tried first. On the Eclipse and Galant with the 4G64 or 4G69 engine, P0171 is frequently caused by a cracked or leaking intake manifold gasket. The intake manifold gasket costs $20-$35 and the repair takes 2-3 hours. On the Lancer with the 4B11 engine, a failing PCV valve or a cracked vacuum hose running to the brake booster can cause a lean condition. On the Montero and Montero Sport with the V6, check for vacuum leaks at the upper intake plenum gasket, as the plenum sits on top of the lower intake and the gasket can dry out and crack with age.

P0300 -- Random/Multiple Cylinder Misfire Detected

P0300 on the Outlander with the 2.4L engine is commonly caused by worn spark plugs or failing ignition coils. Mitsubishi recommends spark plug replacement every 60,000 miles on most four-cylinder engines. Ignition coils cost $25-$40 each aftermarket. On the Eclipse and Galant with the 4G64 engine, carbon buildup on the intake valves is a known cause of misfires, particularly on higher-mileage engines. On the Lancer Evolution with the 4B11 turbo, P0300 can indicate boost system issues including a leaking bypass valve or wastegate malfunction. On the Montero Sport with the 3.0L or 3.5L V6, the distributor cap and rotor (on older models with a distributor) should be inspected -- moisture intrusion into the distributor cap during wet weather is a common cause of intermittent misfires on these engines.

P0340 -- Camshaft Position Sensor Circuit Malfunction

P0340 on Mitsubishi vehicles indicates a loss of the camshaft position sensor signal. On the Outlander and Lancer with the 4B11 engine, the cam position sensor is located at the front of the cylinder head and costs $20-$40 to replace. On the Eclipse and Galant with the 4G63 or 4G64 engine, the cam position sensor is integrated into the distributor on some model years, meaning the entire distributor assembly may need replacement ($150-$250). On engines without a distributor, the standalone sensor is a simple and inexpensive fix. On the Montero Sport with the V6, P0340 can be caused by a failing sensor or by timing belt wear that has allowed the camshaft timing to drift slightly. If P0340 appears on a high-mileage Montero and the timing belt has never been replaced, inspect the belt immediately -- the V6 is an interference engine and belt failure will cause valve damage.

P0420 -- Catalyst System Efficiency Below Threshold (Bank 1)

P0420 on Mitsubishi vehicles typically appears between 80,000 and 130,000 miles. Mitsubishi catalytic converters tend to have a shorter lifespan than some competitors, partly due to the lean-burn calibration on some engines. On the Outlander and Lancer, aftermarket catalytic converters cost $200-$400 and are a straightforward replacement. On the Eclipse with the 2.4L, the catalytic converter is close-coupled to the exhaust manifold, meaning it runs hotter and can fail sooner. Before replacing the converter, check the downstream oxygen sensor ($40-$70) and ensure there are no upstream issues (lean or rich running, misfires, oil consumption) that could damage a new converter. On the Montero Sport with the V6, both Bank 1 and Bank 2 converters may need attention around the same mileage.

P0441 -- EVAP System Incorrect Purge Flow

P0441 on Mitsubishi vehicles indicates the EVAP system purge flow is not within the expected range. On the Outlander, the purge control solenoid valve is the most common cause. This valve is located on or near the intake manifold and costs $30-$50. On the Eclipse and Galant, P0441 can be caused by a cracked charcoal canister or a disconnected vacuum hose between the canister and the purge valve. On the Lancer, the purge valve wiring harness can chafe against the engine where it mounts, causing an intermittent electrical connection. Inspect the connector and wiring for damage before replacing the valve. P0441 does not affect drivability but will cause an emissions test failure.

P0446 -- EVAP Vent System Control Circuit

P0446 indicates a problem with the EVAP vent valve circuit. On Mitsubishi vehicles, the vent valve is typically located near the charcoal canister at the rear of the vehicle. On the Outlander, the vent valve costs $30-$50 and is accessible from underneath the vehicle. On the Eclipse (2000-2012), the vent valve connector is prone to corrosion from road splash, especially in northern climates with road salt. Clean the connector with electrical contact cleaner before replacing the valve. On the Galant, check for a spider web or insect nest inside the vent valve -- this is surprisingly common and can block the valve from operating properly. The vent valve location near the ground makes it vulnerable to debris and insect intrusion.

P0455 -- EVAP System Large Leak Detected

P0455 indicates a significant leak in the evaporative emissions system. On all Mitsubishi models, check the gas cap first -- a loose or worn gas cap seal is the most common cause. Replace the gas cap ($12-$18) and clear the code. On the Outlander, the EVAP system hoses running from the fuel tank to the charcoal canister can develop cracks from heat and age. On the Lancer, the fuel filler neck seal can deteriorate, causing a large EVAP leak that is difficult to detect without a smoke test. On the Eclipse, the charcoal canister itself can crack from parking lot impacts or road debris. A smoke test ($80-$150) is the most efficient diagnostic approach for EVAP leak codes.

P0456 -- EVAP System Very Small Leak Detected

P0456 is the small leak counterpart to P0455 and is common across the Mitsubishi lineup. On the Outlander and Lancer, a worn gas cap O-ring accounts for the majority of P0456 occurrences. On the Eclipse and Galant, the EVAP canister close valve (CCV) can develop a hairline crack that creates a small leak detectable only with a smoke test. On all Mitsubishi models, the EVAP hose quick-connect fittings can loosen over time due to engine vibration, creating small leaks at the connections. P0456 does not affect drivability and is not an urgent repair, but it will cause an emissions test failure. In many cases, simply replacing the gas cap and clearing the code resolves the issue permanently.

P0507 -- Idle Air Control System RPM Higher Than Expected

P0507 on Mitsubishi vehicles indicates the idle speed is above the ECU's target range. On the Outlander and Lancer with electronic throttle bodies, a dirty throttle body is the most common cause. Carbon buildup on the throttle plate prevents it from closing fully. Clean the throttle body with throttle body cleaner ($6-$10) and reset the idle by disconnecting the battery for 15 minutes. On the Eclipse and Galant with the 4G69 engine, a leaking intake manifold gasket or a failing idle air control (IAC) valve ($40-$70) can cause elevated idle. On the Montero Sport, a vacuum leak from the EGR valve gasket or a cracked vacuum hose to the fuel pressure regulator can cause high idle. Always check for vacuum leaks before replacing the throttle body or IAC valve.

P0700 -- Transmission Control System Malfunction

P0700 is a generic transmission flag code that is particularly important on Mitsubishi vehicles equipped with the JATCO CVT transmission. The Outlander (2014-present), Eclipse Cross, and Lancer (2014-2017) use the CVT, which has a mixed reliability record. P0700 on a CVT-equipped Mitsubishi requires reading the specific transmission fault code with an enhanced scanner. Common CVT issues include torque converter shudder, juddering during acceleration, and overheating during sustained highway driving. CVT fluid changes every 30,000 miles (using only Mitsubishi DiaQueen CVTF-J4 or equivalent) are critical for CVT longevity. On older Mitsubishi models with conventional automatic transmissions, P0700 often points to a solenoid failure or the transmission control module needing a software update.

Mitsubishi Model-Specific Issues

The Outlander (2014-present) is Mitsubishi's best-selling model and is generally reliable with the 2.4L engine, though the CVT requires regular fluid changes. The Outlander PHEV adds a plug-in hybrid drivetrain with its own set of hybrid-specific codes. The Eclipse (2000-2012) used the 4G64 and 4G69 four-cylinders in non-turbo models and the legendary 4G63 turbo in the GSX and Spyder GTS -- the turbo models require more attentive maintenance including shorter oil change intervals for the turbocharger. The Lancer (2008-2017) is reliable with the base 2.0L and 2.4L engines. The Lancer Evolution (2003-2015) with the 4B11 turbo is a high-performance platform requiring premium fuel and diligent turbo maintenance. The Galant (2004-2012) is reliable but unexciting, sharing most components with the Lancer. The Montero Sport uses the 3.0L and 3.5L V6 with a timing belt that must be replaced every 60,000 miles -- skipping this service risks catastrophic engine damage.

DIY Tips for Mitsubishi Owners

Mitsubishi vehicles are generally DIY-friendly with accessible engine bays and straightforward component layouts. The 2.4L four-cylinder in the Outlander and Lancer has good access to spark plugs, sensors, and ignition coils from the top of the engine. For OBD-II scanning, any standard scanner reads Mitsubishi powertrain codes. For enhanced diagnostics including CVT-specific codes, the MUT-III (Mitsubishi's dealer tool) or a compatible aftermarket scanner like the Autel MaxiSys is needed. Mitsubishi OEM parts are moderately priced compared to other brands, and quality aftermarket options from Denso (Mitsubishi's OEM supplier for many sensors), NGK (spark plugs), and Standard Motor Products are widely available. For the CVT, always use Mitsubishi DiaQueen CVTF-J4 or a compatible fluid -- generic CVT fluid can cause shudder and premature wear. Join mitsubishiforum.com and evolutionm.net for model-specific advice and DIY guides.

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